MAINTAINERS: remove hugetlb maintainer Mike Kravetz

I am stepping away from my role as hugetlb maintainer.  There should be no
gap in coverage as Muchun Song is also a hugetlb maintainer.

[akpm@linux-foundation.org: update CREDITS]
Link: https://lkml.kernel.org/r/20231220220843.73586-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>